Tomoscope



1961 w. GUNTERT 2,998,518

TOMOSCOPE Filed May 5, 1957 WALTER G NTE R T INVENTOR.

United States Patent 9 i lands Filed May 3, 1957, Ser. No. 656,815Claims priority, application Netherlands May 9, 1956 4 Claims; (Cl.250-65) The invention relates to a. device for examining layers inbodies, particularly the human body, by means of X- rays, gamma rays orthe like. Devices permitting the radioscopy of layers in human bodiesare known and will be referred to in the following description astomoscopes. They generally are provided with a source of radiation and areceiver of radiation which are so arranged as to be synchronicallymoved along paths in different parallel planes, such that the centralray is constantly passing through a fixed point located in the spacebetween said parallel planes and is always directed to one and the samepoint of the receiver surface. Means are provided for observing theradioscopic image formed by the moving receiver as a still tomoscopicimage.

In one known device of the type referred to the receiver surface isformed by the photo cathode of an image amplifier tube, the fluorescentscreen of said tube providing a bright tomoscopic image which may beviewed by means of a system of optical articulations connected to an eyepiece which is fixedly located in space.

Though in some instances satisfactory results may be obtained with atomoscope of the construction described some mechanical and electricalproblems present themselves which are likely to disturb the smoothfunctioning of the device and may give rise to serious failures.

In practice it would be difficult to support the image amplifier tube soas to avoid serious vibrations, even in those cases where the source andreceiver simply describe circular paths. Also the supply of high voltageelectrical energy to the image amplifier tube would constitute a sourceof serious troubles in operation and would necessitate a very carefulmaintenance.

Moreover it will be observed that the image obtained from the curvedphoto cathodes of present image amplifier tubes will correspond to asimilarly curved layer in the body under examination, which isundesirable especially if the image has to be compared with tomographspreviously taken on a flat X-ray film and thus representing flat bodylayers. Another serious drawback is seen in the fact that the photocathodes of presently available image amplifiers are much too small toprovide a tomoscopic image of layers of suflicient lateral dimensions atone time. Therefore much time has to be spent in searching for imageshaving diagnostical value. A still further disadvantage is that theimage forming and transmitting parts of the known device have to bearranged above the patient table thus leaving only a small space for thepatient lying on the table which complicates the operations.

The invention has for its object to overcome the difliculties described.According to the invention the radiation receiver is a fluorescentscreen and an optical system is provided which projects an image of saidfluorescent screen on the photo cathode surface of an image amplifier,which is positioned on the axis of rotation of the tomoscope. Preferablythose parts of the optical system which actually serve the imagery arealso positioned on the optical axis and the lateral displacement betweenthe axes of the fluorescent screen and the photo cathode of the imageamplifier may be realized by two rotating mirrors arranged under anangle with respect to Patented Aug. 293, i961 ice said axes soas toreflect light rays from the screen on to the photo cathode.

The invention will be discussed in some details with reference to thedrawing in which a tomoscope embodying the invention is. schematicallyshown by way of example.

In the drawing 1 is a source of radiation, e.g. an X- ray tube which canbe rotated about the axis 12 by any appropriate means. Said means do notconstitute part of the invention and may be constructed in various wayswhich are well-known to those skilled in the art. Opposite the source 1a fluorescent screen 28 is mounted in a housing 31 which is rotatableabout the axis 12 and is supported by a second housing 35a which isfixedly mounted. Housing 31 contains two flat mirrors 29 and 30 whichreflect light rays emitted by the fluorescent screen 28 so as to enterthe housing 35a. The latter housing receives a mirror objective systemof conventional design, comprising a concave spherical mirror 34, ameniscus shaped correcting lens 33 whose surfaces are concentric to theconcave mirror 34, a lens element 32 having a slightly conical surfacefor further reducing the spherical aberration of the system, and a flatmirror 35 which projects the image of the screen 228 on the photocathode 36 of the image amplifier tube 37.

It will be understood that in operation the source 1 and the fluorescentscreen 28 are moving in parallel circular paths and have in their pathsa phase difference of Thus the central ray of the beam 4 radiated by thesource 1 which always intersects the axis 12 in a fixed point isconstantly striking the fluorescent screen 28 in one and the same point.A well-defined image of the layer indicated by a horizontal arrow of abody which is positioned between the source of radiation 1 and thefluorescent screen 28 will be formed on the fluorescent screen 28 andthe images of layers positioned above or below said first mentionedlayer will fade out due to the constant movement of the source andreceiver.

If the fluorescent screen 28 is fixedly mounted in the housing 3-1 itscharacteristics should be such that the fluorescence of a point of thescreen surface is suppressed abruptly after said point is no longer hitby a ray, otherwise the rotation of the screen would cause blurredimages due to a zone of gradually decreasing brightness following eachline of the image. It is also possible, however, to use slower screens,but then means have to be provided for avoiding relative movements ofthe screen with respect to the image formed on it by the beam 4. Thefixed orientation in space of the screen 28 may be obtained by anyconventional means, such as a set of gears coupling the circular screen23 to the axis of rotation 12.

An image amplifier tube 37 is fixedly arranged with its axis along theaxis of rotation 12 of the tomoscope and is projecting into the opticalsystem through an aperture in the spherical mirror 34, so as to have itsphotocathode located in the image surface of the optical systern. Itwill be observed that the flat mirror 35 serves to reflect the lightrays travelling to the focal surface of the spherical mirror 34 so thatthe image is formed at a location which may conveniently be reached bythe image amplifier.

The image surface (fluorescent screen) 38 of the image amplifier 37 is,in turn, imaged on the photo-sensitive plate 41 of a conventionaltelevision camera by a symmetrical lens system 39, 44) of highluminosity and magnification one. A flat mirror 42 is arranged betweenthe two components 39 and 40 under a 45 angle with respect to theoptical axis 12 in order to reduce the height required for the opticaland electrical apparatus below the image amplifier. The optical systems39 and 40 being identical in construction and forming together asymmetrical objective for 1:1 imagery, the light rays leaving the lenssystem 39 are thus parallel to each other.

It is to be understood that the provision of a television camera forviewing the image formed by the image am plifier 37 is only meant as anexample and clearly' does not present a limitation of the scope of thepresent invention. The fluorescent screen 38 of the image amplifier mayas well be viewed directly by means of a suitable microscope orphotographed, by any suitable camera, if desired.

Furthermore it will be appreciated that, though of course it ispreferred to have the image amplifier as well as the optical imagingsystem made stationary so that only the fluorescent screen 28 and themirrors 29 and 30 have to be moved, it is yet possible to rotate theoptical system or the amplifier or both about the axis 12, withoutgiving up some of the important advantages of the present invention.

What I claim is:

1. A device for producing images of a thin section of a stationaryobject, particularly the human body, comprising a source of X-ray typeradiation disposed on one side of the object, means for moving saidsource along a circular path lying in a first flat plane, a fluorescentscreen disposed on the other side of said object for collecting saidradiation after its passage through said object and converting the sameinto an optical image, means for moving said fluorescent screen insynchronism to said source along a circular path lying in a second flatplane parallel to said first plane, said source and said screen having acommon axis of rotation whereby, in operation, the central ray of thebeam transmitted by said source is constantly passing through a pointfixedly located in the space between said first and second plane and isat any time directed to one and the same point of said screen, an imageamplifier fixedly mounted in said axis of rotation, and an opticalsystem between said screen and said image amplifier for projecting astationary image of said screen on the photo-cathode of said imageamplifier.

2. A device for producing images of a thin section of a stationaryobject, particularly the human body, comprising a source of X- or likeradiation disposed on one side of the object, means for moving saidsource along a circular path lying in a fiat plane, a housing disposedon the other side of said object, means for rotating said housing insynchronism to said source around an axis of rotation perpendicular tosaid plane and passing through the center of said circular path, thewall of said housing having an aperture therein in excentric positionwith respect to said axis of rotation, a fluorescent screen in saidaperture for collecting said X-radiation after its passage through saidobject and for converting the same into an optical image, a pair ofplane reflecting surfaces mounted parallel to each other in said housingat an oblique angle with respect to said axis of rotation so as tosuccessively reflect light rays transmitted by said screen, an imageamplifier fixedly mounted in said axis of rotation of said housing andan optical imagery system in axial alignment with saidimage amplifierfor collecting light rays reflected by said reflecting surfaces andforming a stationary image of said screen on the photo-cathode of saidimage amplifier.

3. A device for producing images of a thin section of a stationaryobject, particularly the human body, comprising a source of X- or likeradiation disposed on one side of the object, means for moving saidsource along a circular path lying in a fiat plane, a rotatable housingdisposed on the other side of said object, the axis of rotation of saidhousing being perpendicular to said plane and passing through the centerof said circular path, means for rotating said housing in synchronism tosaid source, the wall of said housing having an aperture therein inexcentric position with respect to said axis of rotation, a fluorescentscreen in said aperture for collecting said X-radiation after itspassage through the object and for converting the same into an opticalimage, a pair of plane reflecting surfaces mounted parallel to eachother in said housing at an oblique angle with respect to said axis ofrotation so as to successively reflect light rays transmitted by saidscreen, an image amplifier fixedly mounted in said axis of rotation ofsaid housing, an optical imagery system in axial alignment with saidimage amplifier for collecting light rays reflected by said reflectingsurfaces and forming a stationary image of said screen on thephotocathode of said image amplifier, a stationary mount for saidoptical imagery system, and bearing means on said mount for rotatablysupporting said housing.

4. A device for producing images of a thin section of a stationaryobject, comprising a source of X-ray type radiation disposed on one sideof the object, means for moving said source of radiation in accordancewith tomographic motion, a fluorescent screen on the other side of theobject, an image amplifier fixedly mounted in the axis of thetomographic motion, and an optical system between said image amplifierand said fluorescent screen for receiving light rays from saidfluorescent screen and conducting it to said image amplifier, saidoptical system being operatively connected to said means for moving atleast the portion of said optical system adjacent said fluorescentscreen in accordance with the tomographic motion.

References Cited in the file of this patent UNITED STATES PATENTS

